As we celebrate the Melbourne Cup today with our drinks and nibbles, it’s worth a passing glance at the way we nourish our champions of the turf.

Horse nutrition and its impact on horse welfare are part of the debate around what is called ethical racing.

How you feed a racehorse affects its performance. Feed it insufficient high-energy food and it’ll lack the fuel to compete; feed it too much forage (grass or hay) and you’ll weigh it down.

Feeding regimes affect not just performance but also health and welfare. Racehorse rations may meet the horse’s nutritional needs but may leave it with more than a little frustration. To understand why, we need to consider how horses have evolved to feed themselves.

Free range

Free-ranging horses graze for up to 17 hours per day, and are able to move about, selecting habitat that allows them to maximise their intake of high-quality food.

Similarly, in domestic contexts, horses at pasture can enjoy tremendous variability in the shape and quality of paddocks they are offered, which influences the amount of movement required during grazing. It has been estimated that horses at pasture take some 10,000 steps per day.

Horses naturally graze and browse for most of the day and night.Paul McGreevy, Author provided

For competitive purposes, performance horses such as racehorses are usually stabled so that their nutrient intake can be controlled and they can be fed readily digested concentrated foods that are consumed more rapidly than less energy-dense (more natural) forages.

In an effort to reduce the chances of colic (gastro-intestinal pathologies, such as those that led to the scratching of Mongolian Khan from this year’s Melbourne Cup), access to concentrated food is usually restricted immediately before and after strenuous exercise, though it is not clear whether this practice is effective.

But horses have evolved to be trickle feeders. In the free-ranging state, they do not have discrete meals but instead browse and graze as they wander through their home range.

The stomach of an adult horse is relatively small (nine to 15 litres) and inelastic, so it empties within about 20 minutes, depending on the physical qualities of the current meal.

A gut full

Restrictions on feeding behaviour, and especially limiting a horse to discrete meals, can lead to digestive upsets and behavioural frustration. Bulky foods are avoided for racehorses because they fill the gastrointestinal tract, create a thermal load and are thought to compromise lung volume and racing performance.

Furthermore, fibre and the saliva that must be swallowed with it add to the non-functional weight the horse must carry. This means that although their nutritional needs are being met, most high performance horses cannot fulfil their behavioural need to forage and maintain their gut-fill.

For many young thoroughbreds produced for racing, the departure from natural nutrition begins with early weaning from milk to grain so they can begin consuming highly concentrated feeds. These rations help to ensure rapid growth and thus boost foals’ chances of competing successfully within their peer group.

These foals are the hot-house flowers of the horse world. Largely as a result of confinement and intensive feeding, approximately 10% of racing thoroughbreds showed the equine equivalent of obsessive compulsive disorders, called stereotypies.

Roughly half of these behaviours involve repeated locomotory activity (so-called weaving and box-walking) while the remainder are mostly repetitive oral activities (variously called crib-biting and wind-sucking) that give the impression that the horse is gulping air.

Saliva is a natural buffer to excess gastric acidity, but in horses, its production depends on pressure on the parotid salivary gland during chewing. If too little time is spent grazing or chewing forage, not enough saliva may be produced to buffer the stomach contents.

Concentrated feeds and periods without food are associated not only with reduced saliva production and increased gastric acidity but also the risk of gastric ulceration.

The significance of gastric ulceration was recognised in 2008 when a Western Australian report from the Australian Government’s Rural Industries Research and Development Corporation (RIRDC) found ulcers in 53% of racehorses. The prevalence of ulcers increased by 1.7 times for every week the horse had been in training.

A separate study published in 2003 showed that 86% of New South Wales racehorses were affected.

It is a pity these studies have not been repeated to allow us to monitor progress but, for some time now – and understandably – the lion’s share of equine research funding has been channelled into Hendra virus studies.

We need a change

Gastric ulcers and oral stereotypies are the inadvertent side effects of feeding for early maturity and high performance. They’re an industry-wide problem.

Although the solution – to feed horses more naturally – may appear simple, it brings with it the risk of a loss of competitive edge.

The use of permitted medications to resolve gastric ulcers is therefore far more appealing and therefore prevalent. We need ongoing research that monitors that prevalence of these revealing feeding-related disorders.

Plainly, rather than relying on treatments, a more sustainable solution is called for to prevent these disorders in the first place. And a more fundamental question is who should be leading the debate for change?

As discussions around ethical racing continue, the need for a cost-benefit analysis is clear. We cannot change the horse’s gastro-intestinal structure and function but we can feed horses in ways that promote their health and welfare while still racing them.

Those who sponsor racing may soon need to show that the costs horses pay for the sport are mitigated and justified. As part of this process, the industry may wish to benchmark incremental falls in the prevalence of gastric ulceration and oral stereotypies across the racing horse population.

The best trainers will continue to prevail under a system that safeguards horse welfare.